Analysis of synthesis and secretion of expressed scFv 23F-425. The Myc-tagged bispecific protein 23F-425 was radiolabeled in OST7-1 producer cells and analyzed by immunoprecipitation using an anti-Myc antibody. At 0, 4, and 16 h after labeling, equal volume fractions of cell lysate (L) and culture medium (S) were analyzed. The Myc-tagged bispecific scFv s11-42539, 40 was included in the experiment for comparison. The position of the scFv’s is indicated by a dot. At the right, a control analysis of cells transfected without DNA indicates the nonspecific nature of some proteins.